The present invention relates to a garment, more particularly to a garment for applying pressure to a wearer and/or for positioning and applying pressure to transmitters (e.g. tactors or bio-feedback sensors) to press them against the wearer of the garment while accommodating body movement under positive or negative G (gravity pressure).
Loss of situation awareness (SA) and spatial disorientation (SD) are situations encountered for example by aviators and have been blamed for a significant number of aviation mishaps. SD can occur for example when there are missing or conflicting visual cues (e.g. in fog or white-out conditions) or when flight maneuvers greater than 1-G produce a false perception of rotation to the aviator.
The Tactile Situation Awareness System (TSAS), developed by the US Naval Aerospace Medical Research Laboratory (NAMRL) presents 3 dimensional orientation information to pilots and aircrew by taking advantage of an intuitive response produced upon stimulation of skin tactile receptors. TSAS uses for example, electromechanical or pneumatic transmitters generally known as tactors to provide tactile stimuli to the receptors (skin). The tactors produce small, rapid displacements of the skin, typically perpendicular to the skin surface of enough magnitude to excite the receptors. For example, tactile stimuli applied to the pilot""s chest in a fixed-wing aircraft indicate that the nose is going down. In a helicopter, tactile stimuli on the pilot""s right side or back indicate that the aircraft is sliding in those directions, helping the pilot to maintain a stationary hover without reference to the ground or instruments.
To maximize the transduction of the tactile stimuli to the skin receptors, the tactors are normally mounted to provide direct contact between the tactor and the skin of the wearer.
This pressure garment""s primary function is as a tactor locator system (TLS) to maintain tactor position and press the tactor against the skin by providing a counter pressure of sufficient magnitude to ensure transmission of the stimuli. Furthermore, the counter pressure should remain relatively constant to maintain repeatable tactile stimuli. The pressure that can be provided by a close-fitting garment is largely dependent on the local geometry of the body surface. Obtaining sufficient counterforce against the skin is a challenge particularly over concave body sites such as along the sternum between the pectoral muscles and in the lumbar region, which are among the ideal locations for tactor placement.
An inflatable cooling vest (Frim, J. and Michas, R. D. E, U.S. Pat. No. 5,243,706, issued Sep. 14, 1993; Frim, J. and Michas, R. D. E, CA Patent 2051358, issued Mar. 18, 1997) over the upper torso has successfully functioned as a TLS during rotary wing flight testing (Raj, A. K., Suri, N., Braithwaite, M. G., Rupert, A. (1999) The tactile situation awareness system in rotary wing aircraft: Flight test results. RTO HFM Symposium on xe2x80x9cCurrent Aeromedical Issues in Rotary Wing Operationsxe2x80x9d, RTO MP-19. 16-1 to 16-7) however skin contact was minimal and thus the success was limited.
NAMRL has proposed the use of 8 horizontally spaced (along the height of the user) rows of 12 circumferentially spaced (around the body of the user) tactors. The choice of 12 around the circumference of the garment is based on the hour hand of a clock, which has historically been used to describe location/direction. However, the array is not restricted to this configuration but will depend upon the specific needs of the environment in which TSAS is used.
A TLS providing a minimum of 15 grams (g), of tactor counterforce measured at 1 G (gravitational pressure) with an electromechanical tactor-sized load cell i.e. about 3.0 cm diameter and 7.7 mm thickness was deemed xe2x80x9cacceptablexe2x80x9d by NAMRL for intensity of the TSAS signal. Rotary-wing flight-testing of this system demonstrated that the information transmitted to the pilot via TSAS is easily interpreted with minimal training (Raj et al., 1999). In these devices the sensations transmitted to the user via the tactors are computer activated by sending the signals to and from the tactors to a suitable computer.
Counter pressure garments have been used for years to protect blood circulation either during shock (McCabe, F. J., U.S. Pat. No. 5,146,932, issued Sep. 15, 1992) or during exposure to increased gravity by aircrew (Clarke, D. M., CA Patent 672429, issued Oct. 15, 1963). Anti-gravity pressure suits (G protection suits) are worn to counter the effect of blood pooling in the lower limbs during unusual aircraft accelerations. Reddemann, H. et al. (U.S. Pat. No. 5,027,437, issued Jul. 2, 1991) combines G protection with active cooling whereas Bassick, J. W. and Dubois, E. A. (U.S. Pat. No. 5,003,630, issued Apr. 2, 1991) combines G protection with passive cooling via evaporation of sweat through vapour permeable bladders. Pressure garments have also been used to treat various medical conditions such as in the treatment of lymphedema (Kloecker, R. J., U.S. Patent Application 2002/0042585 A1, published Apr. 11, 2002) and to reduce scarring in burn patients (Cheng, J. D., Evans, J. H., Leung, K. S. Clark, J. A., Choy, T. T., Leung, P. C. (1984) Pressure therapy in the treatment of post-bum hypertrophic scarxe2x80x94A critical look into its usefulness and fallacies by pressure monitoring. Burns 10, 154-163.). However, there is no known counter pressure garment that conforms to the varied surface geometry of the body. Close fitting garments made of stretchable material such as that sold under the Trademark xe2x80x9cLycraxe2x80x9d will contact the skin around the circumference of the body but will not have contact over the areas of concave curvature such as along the chest sternum, upper and lower spine.
At 1 G (i.e. normal G) It has been found that a person can sense the skin displacement resulting from a counterforce on the tactor of 15 g. As G increases, a greater counter force is needed to hold the tactor against the skin such that the skin tactile receptors are sufficiently stimulated for the pilot to sense the signal.
The Lycra garments (pressure applying garments used to treat various medical conditions) tested by Cheng et al. (1984) had no pressure in the areas of concave curvature between the shoulder blades and lower back. To address this problem, they filled the body surface crevices under the garments with foam and similar materials to build up the contour and thus obtain pressure against the skin.
While the addition of foam in these pressure garments for treating medical conditions received limited success, this solution (addition of foam) is not satisfactory for use in a TLS garment as it adds insulation and contributes to heat stress in the cockpit. Also with repeated wear, the foam generally becomes less effective in applying pressure against the skin due to compression set.
The use of such stretchable garments is not satisfactory because after only a few hours of wear, stretch garments tend to lose elasticity making them less effective in applying pressure against the skin. Cheng et al. (1984) observed that the Lycra pressure garments they tested lost fabric elasticity and tension, reducing pressure against the skin after a 12 hour period.
Integrating sensors etc. into the garment and using the garment to hold them against the skin, is not a new concept. The xe2x80x98SmartShirtxe2x80x99 is an example (see http://www.time.com/time/2001/inventions/health/insensor.html) however; such a garment cannot for example provide sensor/tactor contact in the concave areas of curvature of the body. Furthermore obtaining a sufficient counter pressure against the tactors/sensors in a high gravity (G) environment (i.e. during aircraft acceleration) is a limitation that the SmartShirt concept is unlikely to overcome.
It is an object of the present invention to provide a garment for mounting tactors in strategic locations relative to the body of the user and for applying the desired amount of pressure holding the tactor against the user.
The main objective of the present garment is to provide tactor counter pressure against the skin over areas of the body that include the torso, upper arms and upper legs and other areas providing concave curvatures to the suit. A second objective is to reduce heat stress of aircrew by the removal of metabolic heat via convective cooling when attached to an air source and via the evaporation of sweat through the vapour permeable fabric of the garment.
The present invention could also be used to apply pressure to reduce scarring in bum patients. Broadly the present invention relates to a pressure applying garment comprising a body enclosing garment formed by a main inflatable bladder composed of opposed interconnected inner and outer walls, means interconnecting said inner and outer walls at spaced locations, means for inflating said main inflatable bladder to a first pressure to press said inner wall toward a wearer and conform said inner wall to contours of said wearer, a plurality of auxiliary inflatable bladders each formed by an inner expandable wall and a cooperating outer wall, said inner expandable wall having its outer surface relative to said auxiliary bladder facing toward said wearer when said wearer is wearing said garment, positioning means fixing said auxiliary bladders in selected positions relative to said garment and thereby said wearer when said garment is worn by said wearer, separate means for inflating at least some of said auxiliary bladders to a selected pressure different from said first pressure to deform said expandable inner wall of its auxiliary bladder to conform with and press towards adjacent portions of said wearer when said garment is being worn by said wearer.
Preferably said inner expandable walls of said auxiliary bladders are formed by portions of said inner wall of said main inflatable bladder.
Preferably said pressure applying garment further includes a plurality of transmitters mounted in spaced relationship at strategic locations on said garment in positions wherein said transmitters are located between said inner wall and said wearer when said garment is being worn by said wearer and pressed toward said wearer when said main inflatable bladder is inflated,
Preferably said pressure applying garment includes further transmitters associated with said auxiliary bladders and interposed between said expandable inner wall of their respective auxiliary bladder and said wearer when said garment is being worn by said wearer so that pressure in said auxiliary bladders force said further transmitters against said wearer.
Preferably, the positioning means of the auxiliary bladders comprises connecting means interconnecting said inner and outer wall of said main bladder around the outer periphery of each of said auxiliary bladders.
Preferably, the connecting means comprises welds.
Preferably, said auxiliary bladders include means to impede expansion of said cooperating outer wall of said auxiliary bladder.
Preferably, wherein said means to impede expansion of said cooperating outer wall of said auxiliary bladder comprises a stiffener panel interposed in said garment in facing relationship to said outer cooperating wall of said auxiliary bladder.
Preferably, said garment further comprises substantially parallel, elongated stiffener elements positioned in space relationship around the circumference of said garment and having their longitudinal axis extending substantially perpendicular to the circumferential direction of said garment.